1. Field of the Invention
This invention is related to the general field of chemical laboratory equipment. In particular, the invention provides a new apparatus, consisting of a beaker heated by a temperature-controlled thermoelectric unit, for use in temperature-sensitive chemical reactions, such as in electroplating of small items like as jewels and lapidary works.
2. Description of the Prior Art
Chemical laboratories require constant-temperature environments for performing experiments under controlled conditions. After reactants are heated to the desired experiment temperature for a given process, it is often critical that the temperature be maintained constant for the duration of the experiment in order to produce meaningful results. Similarly, constant-temperature apparatus is essential for certain types of electrochemical reactions carried out in small production laboratories, such as in the electroplating of jewels and other works. While this disclosure is not intended to be directed only to electroplating, this process will be used for the purposes of describing the invention and illustrating its usefulness.
Electroplating has for its object the deposition of a layer of metal on another metal or nonmetal (such as glass, porcelain, plastic) for the purpose of ornamentation, corrosion protection, building up of worn parts, improving wear resistance, improving light reflectance, or otherwise changing the physical or chemical properties of surfaces. All electroplating on a commercial scale is done in aqueous solutions; the object to be plated is made the cathode, or negative electrode, immersed in a solution containing ions of the metal to be plated. In nearly all cases, the anode or positive electrode, also immersed in the same solution, is made of the same metal as that being deposited on the cathode. As direct current flows between the electrodes, the anodic metal goes into solution electrolytically and replaces the metal ions deposited on the cathode, thus maintaining the metal content of the plating solution. Thus, theoretically the solution should suffer no change in composition with use. In practice, though, there are changes that occur as a function of variables such as the type of metal being deposited and the operating conditions, temperature being one of the most significant of such variables. Therefore, control of the temperature of the electroplating bath is an important feature of electroplating apparatus.
Electroplating performed by jewelers and other small-artifact artisans is normally carried out in rather unsophisticated fashion by heating the electroplating solution to the desired temperature in a conventional beaker over a hot plate. For example, gold plating is typically performed from a gold cyanide solution at 60.degree. to 82.degree. C. The two electrodes are then immersed in the solution and energized by a D.C. voltage source for the required period of time to achieve the desired level of deposition, while the temperature is maintained approximately constant by alternatively switching the hot plate on and off during the electroplating operation.
Obviously, the process of conducting electroplating by immersing and manipulating the object of interest in a beaker sitting on a hot plate, while controlling the bath temperature by turning the plate on and off, is cumbersome, inefficient and impractical. Moreover, since the heat source at the bottom of the beaker, a vertical temperature gradient is created within the solution which may affect the quality of electroplating. Therefore, there exists a need for a simple, temperature-controlled, electroplating container that automatically maintains the plating solution's temperature at the desired set-point.